1. Field of Invention
The present invention relates to an encryption/decryption method. More particularly, the present invention relates to an encryption/decryption method adopting a SHA function.
2. Description of Related Art
Encryption algorithms have been widely used in securing data and protecting privacy in communication. There are many proven asymmetric algorithms as well as symmetric algorithms that are secure and reliable. However, when implementing data encryption in a physical layer of a data transmission medium with an embedded cryptographic module, performance of the cryptographic module must not become the bottleneck of data transmission rate.
Most proven asymmetric algorithms have a high requirement for computation resources and time and are not suitable for encrypting high speed transmission data.
Symmetric algorithms are generally chosen for implementing high transmission speed cryptographic module hardware. Most symmetric algorithms use short fixed length keys and can only encrypt a small block of data at a time. AES (FIPS PUB 197), for example, encrypts a 128-bit data block at a time with a 128, 192, or 256-bit key. However, the security of AES is limited to the 256-bit maximum key length.